Low to No Oil Pressure

[WorkInProgress]

I purchased a 67 vert about 3 months ago. I hired a local shop who was recommended by Dallas Mustang to address some mechanical issues. Some of the stuff was fixed, some was not.

I have done some research of previous post, and I cannot find a post that addresses the issue I am presently having.

Background:
1967 Mustang Convertible
Straight Six 200CI
C4 Tranny

Work done by local repair shop
Replace rear main seal
New oil pan and seal
New oil pump, Melling M65-B
New suspension and steering linkage
Still leaks oil. Shop told me it was impossible to totally eliminate oil leak. I get silver dollar size drops between motor and bell housing after highway driving. Reviewing this board I have learned the local shop was less than truthful with me, as there are several people have successfully eliminated oil leaks. The local shop also told me a high volume oil pump was installed. Via this board I have learned there is no high volume pump available. As a result I no longer believe what the local shop is telling me.

Work Done by me
Pony Carbs 1100
DUI Ignition System
Mechanical oil pressure gauge

Problem:
I am loosing oil pressure once motor reaches normal operating temperature. At cold start up oil pressure is 20 at fast idle If stopped at a stop sign it will drop to 0. At 2000 RPM (driving around speed) it is in the 15 to 20 PSI range. I changed the oil filter, thinking the oil filter might be clogged restricting oil flow and pressure. I pulled the DUI and ran the oil pump with a drill, 3,000 RPM, oil pressure never got over 30. Re-installed DUI, drove car around, same problem, no oil pressure when stopped with tranny in gear, 5 PSI with tranny in park. Limped it home, drained the oil, pulled the oil pan, pulled the oil pump. The oil pick up screen did have some loose RTV on the screen and some back stuff that was a solid, tiny rock size, maybe up to 1/8” in diameter. The black stuff would disintegrate when rubbing a piece between my fingers between my fingers. There was not a lot of stuff on the oil pickup screen. Less than 15% of the screen was obstructed.

The oil pump pressure release valve does not seem to be stuck open. I was able to move it back and forth with a small screwdriver, so I believe it is closed, as the pin that is the stop is hitting the inside of the oil pump. To get the valve to move I have to force a screw driver between the pin and the inside of the pump. Oil pump does look new. Oil pan is new and does not have a lot of sludge in the pan, just a speck or two of the above mentioned black stuff. Bottom end is not super clean, but does not have a tremendous amount of sludge. With the pan removed and the DUI installed I was able to confirm I have oil pump drive shaft at the pump and at the DUI, so I believe the pump is spinning.

Does anyone have an idea as to what I need to do?

Can I safely blow air back through the oil pressure sending unit hole in an attempt to blow out an obstruction?

Is there a way to rooter rooter out the oil passage inside the block?

Is it possible the new Melling pump was bad out of the box?

Several people have commented in other threads that scored bearings can lower oil pressure, but I am having a difficult time understanding how this is possible. The oil pressure sending unit is between the bearings and the pump. In my very small brain, I do not see how main bearings could affect oil pressure at the sending unit.

Any assistance would be most helpful.

Thank you

 

[Vin Man]

Can you clarify for me: are you running a mechanical oil pressure gauge or are you using a sending unit? You refer to both in your post. If you are using a sending unit, have you tried swapping it out? If mechanical, are the lines clear (no kinks)?

Do you notice symptoms of low oil pressure - top end making noise?

 

[ponyrider200]

Do you know how many miles are on that engine? Think of bearing wear as increasing the size of the passage the oil travels through. A small size passage with a constant pressure from the pump will give you greater oil pressure than a larger size passage with the same amount of pumping pressure.
What might help you is to try using a heavier viscosity oil. Try switching to a 15W50. A 10w30 oil in a high mileage, high wear engine can cause a drop in oil pressure. Also, have you done a compression test of your engine? If you have a lot of miles on that engine, causing bearing wear, you may also have a problem with low compression in your cylinders.

 

[BIGREDRASA]

As long as you have the pan off, pull off one of the main bearing caps. Look at the bearing. If you see copper, it and the rest are probably toast. You can actually do an in-frame bearing replacement without too much trouble at this point.

 

[WorkInProgress]

Vin,

When I first noticed the dropping oil pressure it was on the stock gauge with a stock sending unit. Per the advice of the forum, I installed a generic mechanical gauge to know exactly what oil PSI I had. Used the stock sending unit hole to install the mechanical gauge. Tube is clear and not kinked. When spinning with a drill I can watch oil run up the clear tube. Both the stock gauge and the mechanical gauge are indicating the same drop in oil pressure.

There is some interment top end noise, slight ticking from the front of motor. It only happens at idle. Once RMPs reach 1,000 ticking goes away.

Pony,

Odometer reads 38,000, I have no idea the actual mileage is. I have not run a compression test. During the install of the Pony Carb I did connect a vacuum gauge to the intake manifold, and I am pulling 20 inches at 750 RMP. According to the DVD sent to me by Pony Carbs a motor with weak compression will not do this. For what that is worth. I run a compression test and am willing to try 15W50.

Thank you

 

[BIGREDRASA]

Look at the bearings.

 

[WorkInProgress]

BIGRED,

I did pull the main bearing closest to the radiator, under the theory it was the one furthest away from the oil source and as such would look the worst. It is all silver inside where it contacts the crankshaft, no copper is showing. It is not perfectly smooth, there is a small imperfection that looks a lot like pitting.

This is the first time I have ever pulled an oil pan, and a bearing for that matter. Is it possible all the copper has been worn off?


Thank you

 

[rbohm]

8) pull a rod bearing and see what that looks like. main bearings generally have less wear on them than rod bearings do. also get some plastigage, the green kind is what you want, and check the bearing clearances, they should be between .0015 and .003". wider than that and you are losing pressure due to excessive bearing clearance.

 

[69.5Mav]

WorkInProgress

Lots of good sugestions here.

The pump puts out a stream of oil at a pressure that is set by the mechanical qualities of the pump. As you constrict the flow the pressure will rise to maintain the flow. When the pressure reaches the level of the relief valve it will bypass some of the flow to keep the pressure from riseing to high and blowing something ( the weakest point) out. If the clearance on the bearnings is to big then too much oil will flow past them and pressure will not build as high as it should.

One thing you could try is to get a big pan, a bucket and a new oil pump, new pump can indide be bad out of the box and you may not have gotten a new pump in the first place. Istall the pump, put the big pan under the engine, rout the oil pump pick up over to the pan full of oil and spin the oil pump. Look for oil dring out of bearings and other places and check that oil pressure. If the oil pressure jumps up you had a bad oil pump if not any of the rod or main bearing that are leaking more then the rest are a good place to start.

Thicker oil may help a little but is only a stop gap messure to buy some time to fix the real problem as it will continue to degrade.

Any way just my two cents worth. Hope it helps.

 

[rbohm]

8) another thing to check is make sure the pump is not drawing air from someplace in the system. check the pick up tube for cracks, and check the gaskets for possible leaks. this dawned on me when i was helping a friend of mine with a different problem, that of the fuel pump not being able to draw fuel from the tank. turned out it was a bad hose. oh and just because the check valve has good spring pressure does not mean the valve is sealing properly.

 

[WorkInProgress]

OK,

I now understand how loose bearings can reduce oil pressure. No constriction beyond sending unit. No constriction equates to possible oil volume, but not enough pressure to get to all the places the oil needs to go.

Ran a dry compression test under the following conditions:
Pulled DUI
Removed all spark plugs
Pan off
Battery hooked up to charger with start setting. Battery was getting weak.
Screw driver holding open choke and butterfly.
All 6 cylinders are between 180 and 190. Sometimes the gauge would jump to over 200 but at the end of spinning the starter gauge was between 180 and 190.

A thought just occurred to me, by running a compression test with no pan and no oil did I do further damage to the block, rings, or cylinder walls?

I bought some green plastiguage. According to the test I ran on the main bearing closest to the radiator, the stuff barley got mashed. To small register on the chart.

I pulled the #2 rod bearing and ran the same test with plastiguage. Result was a much wider bead, about half of the .003 width, but still out of tolerance. There was no scoring or imperfections on the rod bearing as seen on the main bearing.

Per further inspection, the oil leak appears to have been coming from the rear of the pan, not the rear main seal. I removed the piece of sheet metal covering the flywheel, (I think this is called the inspection cover) and there was very little oil on the inside of the inspection cover, but lots of oil on the engine side. Also, there was oil above the rear rubber oil pan gasket. So I think I may be OK with the rear main seal.

Couple of questions:

What are the opinions of using Permatex “The Right Stuff” as an oil pan gasket?

What are the opinions of my rear main seal theory?

What is the best way to remove old oil pan gasket material?

Is it possible to reinstall a main bearing incorrectly resulting in an inaccurate plastiguage reading? I did this test three times with the same result, but I had a heck of a time lining up the bearing and cap. How easy is it to install the bearing wrong. For some reason it did not feel right. I am pretty sure I put it on the right direction, as it has an arrow, and the bearing has little notches to assist the idiot with proper alignment. But when I would put the bearing in the cap it was not tight, but would move around side to side a bit. And I bought a torque wrench from Sears to ensure I got the right torque.

If I put the pan back on, run thicker oil how long can I expect to get away with it?

Once again, any assistance is greatly appreciated.

Thank you,

James

 

[rbohm]

8) the main caps have a slight interference fit in their registers to make sure they are properly located side to side. most engine builders use a plastic faced mallet to get them into place before they torque the main bolts. that said however it sounds like either your engine is worn out, or someone installed the wrong bearings in the motor. perhaps the crank was ground undersize and standard bearings were installed.

 

[Vin Man]

What are the opinions of using Permatex “The Right Stuff” as an oil pan gasket?

James

I think this stuff is great. I used it for oil pan and valve cover (among other places). Definitely seals better than anything else.

 

[JackFish]

So... what brand is this "high volume"/(low pressure) oil pump?
That's where I would start, by replacing it.
Maybe it's a normal one they "modified", or "fixed".

 

[fordconvert]

No reading on the plastigauge on a main bearing seems like we found the problem. No pump is going to be able to maintain a decent pressure if there is that much clearance. With that much clearance there are going to be other issues soon.

 

[69.5Mav]

All 6 cylinders are between 180 and 190.

With reading like those I would not start disasembling the block yet.

Pan off

Pulled DUI

You are probly ok but don't do it any more. There is some oil in the bearings but it won't last long. with the distributer out the oil pump won't spin.

#2 rod bearing and ran the same test with plastiguage. Result was a much wider bead, about half of the .003 width

Assuming you have no crank damage, get some bigger Plasti gage and find out what your clearance realy is. Then subtract the clearance you need from the clearance you have to get the oversize of the bearings.

Bearings are available in oversizes. Check what the plasti gage shows for clearance with the new bearings. In cases where you are just a little out of tolerance you can mix and match the bearing from the same set to see if you can find a pair that works.

For the main Bearing you will need a tool to get the upper half out. Its a pin that fits in the oil hole and pushes the upper bearing out as you rotate the crank.


When you get all the new bearings in, you can pre oil the engine by spinning the oil pump with a drill for at least 15 minuets. You should now get good oil preasure. If so and all else appears ok you can attempt to start the engine.

Good Luck and take all the time you need to do this job right.

 

[WorkInProgress]

Rbohm,
Is a plastic mallet and a rubber mallet the same thing? I have never seen a plastic mallet, but that does not mean one does not exist.

JackFish,
I have purchased a new oil pump from NAPA. It looks exactly like the “high volume” pump that was in the engine. Upon inspection the pump that was in the engine looks new. I believe the pump was replaced, but the tech that did it exaggerated on what he had done.

69.5Mav,
I will get some larger Plasti and run additional test. I inspected the crankshaft at the main bearing closest to the radiator, and there is some scoring on the crank. I ran my finger across the scoring, and I can feel it with my fingertips. I know this is an impossible question to answer, but is it there a rule about how much scoring/imperfections the crank can have before installing smaller bearings is a waste.

I would like to thank every for all of the suggestions and support. There are lots of good people here, I greatly appreciate the help. Happy Turkey Day to everyone.

James

 

[rbohm]

Rbohm,
Is a plastic mallet and a rubber mallet the same thing? I have never seen a plastic mallet, but that does not mean one does not exist.

nope, two different animals. check out lowes, or other hardware stores, or harbor freight. they all carry the plastic faced mallets.

69.5Mav,
I will get some larger Plasti and run additional test. I inspected the crankshaft at the main bearing closest to the radiator, and there is some scoring on the crank. I ran my finger across the scoring, and I can feel it with my fingertips. I know this is an impossible question to answer, but is it there a rule about how much scoring/imperfections the crank can have before installing smaller bearings is a waste.

if you can feel the scoring with your fingernails, you have too much. it is time to pull the crank and have it checked over at a machine shop, and possibly reground.

 

[69.5Mav]

if you can feel the scoring with your fingernails, you have too much. it is time to pull the crank and have it checked over at a machine shop, and possibly reground.

I agree with "rbohm" in principle. However in the real world we sometime accept compromises due to concideration other then purley mechanical ones. You may not be ready or have enough money to do what would amount to a full engine rebuild. Bearing are cheap. Try changing them out. You may get luckey and the engine may last for awhile. All this is predicated on the assumption the the crank journels are not to bad. Your the man on the scene. Examin each bearing and repoert what you find. If you have mostly good ones with just a few with slight scoreing on them you could give it a try. If it does not work out your only out about 40-50 dollars for bearings . The fact that you have such good compression shows that some one did some work on this engine. When using the plasti gage on the scored journals you will get a varying with spread. Try to make sure that the widest part matches the min clearence and the narrowest part matches the max clearence.

 

[rbohm]

if you can feel the scoring with your fingernails, you have too much. it is time to pull the crank and have it checked over at a machine shop, and possibly reground.

I agree with "rbohm" in principle. However in the real world we sometime accept compromises due to concideration other then purley mechanical ones. You may not be ready or have enough money to do what would amount to a full engine rebuild. Bearing are cheap. Try changing them out. You may get luckey and the engine may last for awhile. All this is predicated on the assumption the the crank journels are not to bad. Your the man on the scene. Examin each bearing and repoert what you find. If you have mostly good ones with just a few with slight scoreing on them you could give it a try. If it does not work out your only out about 40-50 dollars for bearings . The fact that you have such good compression shows that some one did some work on this engine. When using the plasti gage on the scored journals you will get a varying with spread. Try to make sure that the widest part matches the min clearence and the narrowest part matches the max clearence.

8) you are right mav, perhaps i should clarify a bit, i have used cranks with scoring i could feel, but my nails would not catch on the scoring. if my nails caught on the scoring, i would not reuse the crank as is. i think the first thing to do is determine just how deep the scoring is, light scoring, where your fingernail skips over it easily, you can just use new bearings. if your nail catches though, regrind the crank. the next thing you need to do is measure the journals with a dial caliper or micrometer and compare that number with what the factory says the journal size should be. you can then get bearings that fit properly.